The present invention relates generally to an improved grade measurement device. More particularly, the present invention relates to an improved grade measurement rod having a base and a support member movably connected to each other.
When constructing a building, road, or the like, it is important that a contractor be able to establish a level surface. To accomplish this task, surveying or grade measurement rods have been used together with a transmitter operable to produce a radiant energy beam, e.g., a laser beam or sound beam. The grade measurement rod includes a detection mechanism operable to detect the radiant energy beam, e.g., a photocell or sound detection device.
In use, a contractor establishes a horizontal reference position by placing the device operable to produce the radiant energy beam at a selected horizontal position. The radiant energy beam establishes a plane a predetermined distance above the base surface from which variations are measured. The device operable to produce the radiant energy beam may be positioned anywhere within the construction area as long as there are no obstructions between the radiant energy beam and the detection mechanism. The detection mechanism is then positioned at the same height above the base surface as the device operable to produce the radiant energy beam. In this manner, the detection of the radiant energy beam indicates that a level plane extends between the two positions. If the detection mechanism fails to detect the radiant energy beam, an angled surface exists between the two positions. A contractor then manually adjusts the detection mechanism by releasing it from the support structure and sliding it up or down until the radiant energy beam is detected. A scale adjacent the detection mechanism is used to indicate the relative distance that the detection mechanism has been adjusted thereby providing a measurement of the relative vertical distance between the two positions. Using this information, the contractor can adjust the base surface as needed in order to provide for a level surface.
One example of a previous survey system is disclosed in U.S. Pat. No. 3,314,068 issued to Verive. In Verive, a transmitting antenna is positioned at a selected point. The radiant energy beam is transmitted at a predetermined height above the base surface. A receiving device is movably attached to a gauge pole and positioned a selected distance away from the transmitter. The receiving device can be slidably adjusted on the pole in order to be raised or lowered to a new height. This relative adjustment indicates the relative vertical distance between the plane defined by the radiant energy beam and the receiving device. The disclosed receiving device includes a handle in order to provide for the vertical adjustment of this device on the pole.
However, a significant disadvantage exists in the prior grade measurement devices. In particular, the adjustment mechanism on the receiving device can be somewhat cumbersome to operate in the field. If the plane being measured by the rod is not level, it can be difficult and cumbersome for a contractor to hold the rod and simultaneously release and adjust the positioning of the detection mechanism. Accordingly, there is a need for an improved grade measurement rod having a receiving device that may be easily adjusted from a first height to a second height.